A card edge connector assembly is adapted for mounting on a printed circuit board to electrically connect with a daughter card. The connector assembly includes a dielectric housing defining a longitude direction, a transverse direction perpendicular to the longitude direction and a slot extending from a mating face thereof along the longitudinal direction, a number of terminals respectively disposed at opposite sides of the slot and a retainer aligned with and spaced from the dielectric housing along the longitudinal direction. The retainer includes a flexible arm extending away from the dielectric housing. The flexible arm is formed with a projection for locking the daughter card in position.